The invention relates to a needle guiding device for a portable, single-thread chain stitch, bag closing machine with a movable needle guiding device.
One form of movable needle guiding device in a portable bag closing machine is disclosed in U.S. Pat. No. 2,960,946, wherein the needle guide is secured by means of a screw to a pivotable holder which also carries a lower feed dog. Thus, this needle guiding device performs a pivoting movement corresponding to the pivoting movement of the lower feed dog. The chain stitch is formed, inter alia, by a large sliding movement of a looper transversely to a feed direction of a workpiece and by a small pivoting movement of the looper in the feed direction of the workpiece. Although this movement of the looper is advisable and advantageous for forming a two-thread double chain stitch, formation of a single-thread, single chain stitch with the same looper drive mechanism additionally requires a special loop retainer which is mounted on the underside of the throat plate. The purpose of the loop retainer is to spread out a needle thread loop located on the looper, in order that the needle can pass through the needle thread loop. The loop retainer has to be adjusted very accurately and, since it comes into engagement with the sewing thread during the formation of each stitch, it is subjected to a certain amount of wear which can lead to undesirable faulty stitches.
In the case of hand-guided bag closing machines, there is generally the risk that the needle of the bag closing machine will be unintentionally subjected to transverse stress when closing bags, which may lead to damage to, or even fracture of, the looper.